Pathology Associates Of Lexington, P.A.

AMA test, blood

Anti-mitochondrial antibody (AMA) is an autoantibody which has been said to be found in some liver diseases...generally accepted as a marker of primary biliary cirrhosis (PBC). We use the FLUORO-KIT test system with cryostat sections of rat kidney and stomach, and or rat liver as the substrate at a beginning dilution of patient's serum of 1:20. The use of animal tissue avoids interference from HLA and/or blood group Abs that may occur were human substrate used. Incidental Abs may show up in this system such as ASMA, APCA, ANA, ARA, ABBA, anti-canalicular Ab, anti-liver cell membrane Ab, and anti-ribosomal Ab. [see table] Mitochondria stain in parietal cell, hepatocytic, and renal tubular cell cytoplasms. There are false positives such that: <1:40 represents "probable nonspecific reactivity"; 1:40 is a "nonspecific positive reactivity"; 1:80 is "significant serologic positivity, PBC?" We have documented instances of levels >1:160 that were not PBC...so, liver biopsy findings are crucial to proper total case interpretation. This antibody can be detected in DIF/DFA skin biopsy preps [S-03-8966].

Associations with undetectable Ab:

normalcy
watch out for cases of AMA negative and ANA positive...may be autoimmune cholangitis if liver biopsy shows chronic portal triaditis and ductopenia.
viral hepatitis¹

Associations with elevated levels:

PBC in 75-95% of cases¹; at 1:160-1:6000 (other diseases at lower levels) and do not correlate with either severity of disease or response to immunosuppressive therapy.²; once the test is reactive at 1:160 or higher, it indicates "significant serologic evidence suspicious for primary biliary hepatitis/cirrhosis" [LMC-01-2794, LMC-01-1280; LMC-02-3489; LMC-02-4906]
autoimmune (chronic active²) hepatitis 0-30% of cases¹
AMA positive PLUS PBC histology BUT with clearly elevated LFTs and other evidence of chronic active hepatitis might be a PBC-AIH overlap syndrome
primary sclerosing cholangitis (PSC) is AMA positive in <5% of cases
extra-hepatic biliary obstruction 0-5% of cases¹
non-obstructive biliary tract disease²
hepatic malignancy²
collagen vascular diseases²
cryptogenic cirrhosis 0-25% of cases¹
drug induced hepatitis 50-80% of cases¹
false pos. = to, > 1:160 in : NASH [LMC-02-3489];

REFERENCES:

A B C's of Interpretive Laboratory Data, 2nd Ed., Seymour Bakerman, MD, PhD, 1984
Lex. Med. Lab. procedure manual and its references as of 7/01